Differential stress-induced regulation of two quinone reductases in the brown rot basidiomycete Gloeophyllum trabeum
Differential stress-induced regulation of two quinone reductases in the brown rot basidiomycete Gloeophyllum trabeum
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DOI：
10.1128/aem.70.1.324-331.2004
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发表时间：
2004-01-01
影响因子：
4.4
通讯作者：
Hammel, KE
中科院分区：
文献类型：
--
作者：
Cohen, R;Suzuki, MR;Hammel, KE
醌还原酶（QRDs）在引起木材褐腐的担子菌密粘褶菌（Gloeophyllum trabeum）中有两个重要功能。首先，需要一种醌还原酶通过密粘褶菌的两种胞外代谢物2,5 - 二甲氧基氢醌（2,5 - DMHQ）和2,5 - 二甲氧基 - 1,4 - 苯醌（2,5 - DMBQ）之间的氧化还原循环产生生物降解性羟基自由基。其次，由于2,5 - DMBQ具有细胞毒性而2,5 - DMHQ没有，所以需要一种醌还原酶将这些代谢物的细胞内库维持在还原形式。鉴于它们在密粘褶菌代谢中的重要性，醌还原酶可能被证明是新型木材防腐剂的有用靶点。我们已经鉴定出密粘褶菌的两个基因，每个基因都存在两个密切相关的、可能是等位基因的变体，它们编码黄素氧还蛋白家族中的醌还原酶。过去对QRD1的研究以及本研究中QRD2的异源表达证实，这两个基因都编码依赖NADH的、含黄素的醌还原酶。对液体培养和木材培养的实时逆转录PCR分析表明，qrd1的表达在次生代谢期间达到最大值，与2,5 - DMBQ的产生同时发生，并且受到诸如醌等化学应激物的适度上调。相比之下，qrd2的表达在2,5 - DMBQ水平较低的真菌生长期间达到最大值，但受到化学应激或热激显著上调。预先用一种具有细胞毒性的醌诱导后，密粘褶菌菌丝体裂解物中的总醌还原酶活性显著增强。qrd2的启动子可能含有抗氧化、异生物质和热激元件，而qrd1中没有，这可能解释了qrd2转录对压力的更大反应。我们从这些结果中得出结论，QRD1是密粘褶菌在木材初期腐烂过程中常规用于解毒醌的酶，并且它也可能驱动生物降解性醌氧化还原循环。然而，当菌丝体受到压力时，QRD2起着更重要的作用。
Quinone reductases (QRDs) have two important functions in the basidiomycete Gloeophyllum trabeum, which causes brown rot of wood. First, a QRD is required to generate biodegradative hydroxyl radicals via redox cycling between two G. trabeum extracellular metabolites, 2,5-dimethoxyhydroquinone (2,5-DMHQ) and 2,5-imethoxy-1,4-benzoquinone (2,5-DMBQ). Second, because 2,5-DMBQ is cytotoxic and 2,5-DMHQ is not, a QRD is needed to maintain the intracellular pool of these metabolites in the reduced form. Given their importance in G. trabeum metabolism, QRDs could prove useful targets for new wood preservatives. We have identified two G. trabeum genes, each existing in two closely related, perhaps allelic variants, that encode QRDs in the flavodoxin family. Past work with QRD1 and heterologous expression of QRD2 in this study confirmed that both genes encode NADH-dependent, flavin-containing QRDs. Real-time reverse transcription PCR analyses of liquid- and wood-grown cultures showed that qrd1 expression was maximal during secondary metabolism, coincided with the production of 2,5-DMBQ, and was moderately up-regulated by chemical stressors such as quinones. By contrast, qrd2 expression was maximal during fungal growth when 2,5-DMBQ levels were low, yet was markedly up-regulated by chemical stress or heat shock. The total QRD activity in lysates of G. trabeum mycelium was significantly enhanced by induction beforehand with a cytotoxic quinone. The promoter of qrd2 contains likely antioxidant, xenobiotic, and heat shock elements, absent in qrd1, that probably explain the greater response of qrd2 transcription to stress. We conclude from these results that QRD1 is the enzyme G. trabeum routinely uses to detoxify quinones during incipient wood decay and that it could also drive the biodegradative quinone redox cycle. However, QRD2 assumes a more important role when the mycelium is stressed.